We propose to identify genes in bone cells that respond specifically to the localized production of human growth hormone (hGH) in marrow. The differential display polymerase chain reaction (DD-PCR) technique will be employed to select and clone cDNAs that are activated or repressed in HS2+BetachGH transgenic mouse bones compared to normal bones. The bones of the transgenic mice have more density, increased cortical thickness, and enhanced biomechanical qualities compared to their controls. Our approach will identify genes that experience major changes in their expression as a consequence of transgene expression: genes that are already known or predicted, as well as those that have not previously been characterized or associated with osteogenesis. The particular relevance of each gene to alveolar bone deposition will be confirmed. Identification of the genes acting downstream of the growth hormone stimulation is critical to understanding the mechanism of the effect and ultimately transferring this technology to clinical applications.